A078438 a(n) = least positive integer solution k to h(k) = h(k-1)+h(k-2)+...+h(k-n), where h(n) is the length of n, f(n), f(f(n)), ...., 1 in the Collatz (or 3x + 1) problem. (The earliest "1" is meant.)

13, 6, 235, 342, 41, 5735, 90746642

Offset

1,1

Comments

1. Recall that f(n) = n/2 if n is even; = 3n + 1 if n is odd. 2. Problem: Is a(n) defined for all n, that is, does a positive integer solution k to h(n) = h(k-1)+h(k-2)+...+h(k-n) always exist?

Links

Table of n, a(n) for n=1..7.

Example

k = 235 is the least k satisfying h(k) = h(k-1)+h(k-2)+h(k-3), so a(3) = 235.

Crossrefs

Sequence in context: A160247 A300886 A301496 * A225954 A133723 A324279

Adjacent sequences: A078435 A078436 A078437 * A078439 A078440 A078441

Keyword

more,nonn

Author

Joseph L. Pe, Dec 31 2002

Extensions

a(7) from Donovan Johnson, Nov 14 2010

Status

approved